The present invention relates generally to optical imaging devices, and more particularly to a novel optical image intensifier tube.
Image intensifier tubes (also called image enhancement tubes or simply image tubes) were first developed in the mid to late 1930's for military night vision applications. The early electro-optical low-light amplifiers were image converter infra-red tubes, also known as Gen O and Gen I night amplifier tubes. These were used successfully for many years. A successor to these tubes was the microchannel intensifier. It was a great improvement in size, cost and performance. A microchannel intensifier tube basically consists of a photo-sensitive cathode, a microchannel plate (MCP), and a phosphor output screen. The photocathode converts incoming photons representing an image to a corresponding stream of electrons. The electrons are accelerated to an MCP which intensifies the flow of electrons. At the output of the MCP the intensified electrons are accelerated again by another strong electric field to strike the luminescent phosphor screen whereat an enhanced visible image is created. The MCP consists of a two-dimensional array of miniature microchannel multipliers. A good background description of the microchannel image intensifier and the fabrication of microchannel plates can be found in "The Microchannel Image Intensifier," The Scientific American, Vol. 245 (November 1981) pp. 46-55 by Michael Lampton.
Microchannel image intensifiers are frequently employed today in applications requiring high amplification of extremely low-light levels. One obvious advantage of the current generation of microchannel image intensifiers is their light sensitivity obviating the need for auxiliary irradiation either in the visible or near-infrared spectrum. They are particularly suited to night-time surveillance in military or police applications since they have high luminous gain, high image resolution and excellent low light sensitivity. In addition the Gen III tubes are particularly sensitive in the near-infrared (NIR) spectrum, which makes them useful in surveillance since night sky radiation is particularly high in the non-visible NIR region.
This invention is directed to an intensifier tube design that reduces costs for such tubes and improves lifetime and reliability.
Another general object of the invention is to provide a low cost image intensifier tube design that greatly reduces major sources of gas leaks in prior art tubes and greatly extends the shelf life of the intensifier tube resulting in lower system maintenance costs in connection with systems employing such tubes.